CN111826201A - A process, system and application for biomass flash pyrolysis gasification and tar removal - Google Patents

Abstract

The invention discloses a process, a system and application for biomass flash pyrolysis gasification and tar removal, wherein the system comprises: a settling furnace for providing an environment for biomass pyrolysis; the feeding machine is arranged at the top of the settling furnace; the gas distribution system comprises a first primary air channel, a second primary air channel and a secondary air channel, wherein the first primary air channel is a nitrogen channel and is communicated with the top of the sedimentation furnace; the second primary air channel is a mixed gas channel of nitrogen and active gas and is communicated with a first air inlet on the side surface of the settling furnace, the first air inlet is arranged on the upper part of the settling furnace, and the active gas is a mixed gas of oxygen, water vapor and carbon dioxide; the secondary air channel is a mixed gas channel of nitrogen, oxygen, water vapor and carbon dioxide, and is connected with a second air inlet on the side surface of the settling furnace, and the second air inlet is arranged at the lower part of the settling furnace.

Description

A process, system and application for biomass flash pyrolysis gasification and tar removal

technical field

The invention belongs to the technical field of comprehensive utilization of biomass resources, and in particular relates to a process, system and application for biomass flash pyrolysis gasification and tar removal.

Background technique

The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not necessarily be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person of ordinary skill in the art.

At present, the world is facing problems such as energy shortage and serious environmental pollution. How to effectively utilize clean and recyclable biomass resources is one of the best solutions to achieve sustainable development and solve development problems. China is very rich in biomass resources, with an annual output of about 5 billion tons and a total energy of up to 6×10 ⁸ tons of standard coal. How to efficiently and cleanly convert biomass into raw materials for energy production is one of the hot topics in current research.

In today's society, the energy crisis is getting worse day by day, and the excessive utilization of coal and oil has also caused serious environmental pollution problems. Effective utilization of biomass energy is one of the optimal solutions for sustainable development and solving energy and environmental problems. my country is very rich in biomass resources, and how to efficiently and cleanly utilize a large amount of biomass resources is one of the hot topics in current research.

Using biomass energy to generate electricity through biomass power plants is one of the most common ways of biomass utilization. Traditional biomass power plants use direct combustion to generate electricity and generate heat, but the calorific value of biomass raw materials is generally low. In addition, the volatile content of biomass is high, and the volatile content of biomass air-dry base accounts for about 75%. During the combustion process, a large amount of tar will be generated. On the other hand, it will also adhere to the surface of biomass raw materials, preventing it from being completely burned out, and further reducing the calorific value.

Biomass pyrolysis gasification is an important way to rationally utilize biomass resources. Biomass pyrolysis gasification is divided into slow pyrolysis and rapid pyrolysis. Slow pyrolysis takes a long time and the process is complicated, while rapid pyrolysis takes less time. , the process is simple, and it is one of the thermal conversion technologies with the most development potential for the utilization of biomass resources. Flash pyrolysis is the fastest method in rapid pyrolysis. Through extremely high heating rate and relatively high temperature, the pyrolysis process of biomass is completed within 3-10s. The products of pyrolysis are mainly fixed carbon and volatile gas, and the yield of tar is relatively low, which is a method of great practical value.

The tar produced in the biomass pyrolysis process is easy to cover the surface of the product and the pyrolysis equipment, resulting in a decrease in the yield of the product, corrosion of the equipment, and environmental pollution. Remove the resulting tar.

Tar removal technology mainly includes physical separation and removal, thermochemical catalytic cracking removal, thermochemical high temperature cracking removal and plasma removal technology. Among them, the thermochemical pyrolysis removal technology is the optimal technology choice for the removal of tar in the rapid pyrolysis process. The high-temperature pyrolysis tar removal technology makes the macromolecular tar components into small molecular gas products through the molecular chain scission and decomposition reaction by creating a high temperature environment. The research results reveal that the temperature has a significant effect on the thermal cracking process of tar. With the increase of temperature, the conversion rate of tar cracking and the yield of gas products will gradually increase. In addition, by adjusting the process parameters of the rapid pyrolysis process, the ratio and composition of biomass pyrolysis gas phase/liquid phase/solid phase products can be adjusted.

Some existing tar removal technologies (such as physical separation removal, thermochemical catalytic cracking removal and plasma removal technology, etc.) need to add corresponding devices or catalysts, which greatly increases the production cost and the complexity of the system. The chemical high-temperature pyrolysis removal technology is more suitable for the rapid pyrolysis process, and needs to provide a sufficiently high temperature and a fast reaction rate. The current gas atmosphere of the slow pyrolysis process is not conducive to the cracking and removal of tar.

SUMMARY OF THE INVENTION

In order to solve the technical problems existing in the prior art, the purpose of the present invention is to provide a process and system for biomass flash pyrolysis gasification and tar removal. The process has the advantages of wide source of applicable raw materials, short time consumption, low energy consumption, high ratio of gas-solid products and low tar yield.

To achieve the above purpose of the invention, one or more embodiments of the present invention disclose the following technical solutions:

In a first aspect, the present invention provides a system for biomass flash pyrolysis gasification and tar removal, including:

Settling furnace, providing environment for biomass pyrolysis;

The feeder is arranged on the top of the settling furnace;

The gas distribution system includes the first primary air channel, the second primary air channel and the secondary air channel, and the first primary air channel is a nitrogen channel, which is communicated with the top of the settling furnace;

The second primary air channel is a mixed gas channel of nitrogen and active gas, which is connected to the first air inlet on the side of the settling furnace. The first air inlet is arranged on the upper part of the settling furnace. mixed composition;

The secondary air passage is a mixed gas passage of nitrogen, oxygen, water vapor and carbon dioxide, and the secondary air passage is connected with the second air inlet on the side of the settling furnace, and the second air inlet is arranged at the lower part of the settling furnace.

In the second aspect, the present invention provides a process for biomass flash pyrolysis gasification and tar removal, comprising the following steps:

The biomass powder is blown into the settling furnace with nitrogen as the first air;

Pass the mixed second air of nitrogen, oxygen, water vapor and carbon dioxide into the upper part of the settling furnace;

In the settling furnace, under the set temperature, the biomass powder is in an active atmosphere, the biomass powder completes high-temperature flash pyrolysis, and volatilization is analyzed;

The precipitated volatiles move downward, and under the action of the mixed secondary air of nitrogen, oxygen, water vapor and carbon dioxide introduced into the lower part of the settling furnace, thermochemical high-temperature cracking occurs, and macromolecules are cracked into small hydrocarbon gas molecules.

In a third aspect, the present invention provides the application of the biomass flash pyrolysis gasification and tar removal process or system in the gas supply of biomass power plants.

Compared with the prior art, the above one or more technical solutions of the present invention have achieved the following beneficial effects:

1) The technological process of biomass flash pyrolysis gasification and tar removal was optimized. Biomass gas-solid products are produced by flash pyrolysis in a settling furnace, and the tar produced is greatly reduced after thermochemical high-temperature cracking, which is extremely beneficial to the subsequent comprehensive utilization of gas-solid products.

2) Using flash pyrolysis to prepare gas-solid products, the preparation time is short, the atmosphere conditions and equipment are simple, and the energy consumption is low.

3) Using biomass powder as raw material, a higher heating rate (1200-1650K s-1) can be used, and the flash pyrolysis only needs to be completed within 3-10s of staying in the furnace, which reduces the production time and cost. It has strong adaptability to biomass, and all types of biomass can be used as raw materials.

4) The biomass gas-solid products prepared have high calorific value and can be used as raw materials for subsequent production, and fixed carbon as a by-product also has high value.

5) The yield of biomass gas-solid product is high, the gas yield is 50-80%, the yield of fixed carbon is 16-26%, and the impurities in the product are less.

6) The comprehensive utilization of biomass is further strengthened. The cracking of tar improves the availability of biomass and reduces the generation of waste and polluting gas in the process of biomass utilization.

7) Passing the pyrolysis gas produced by flash pyrolysis into the boiler of the power plant as gas combustion can solve the problems of unstable raw materials, bad combustion conditions, and serious corrosion of the heating surface in the direct combustion of biomass in biomass power plants. clean and efficient production.

Description of drawings

The accompanying drawings forming a part of the present invention are used to provide further understanding of the present invention, and the exemplary embodiments of the present invention and their descriptions are used to explain the present invention, and do not constitute an improper limitation of the present invention.

FIG. 1 is a schematic structural diagram of a biomass flash pyrolysis gasification and tar removal system according to an embodiment of the present invention.

In the figure, 1. Biomass source, 2. Gas distribution system, 3. Rotary feeder, 4. Settling furnace, 5. Cyclone separator, 6. Gas-solid product collection device.

Detailed ways

It should be noted that the following detailed description is exemplary and intended to provide further explanation of the invention. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

It should be noted that the terminology used herein is for the purpose of describing specific embodiments only, and is not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly dictates otherwise, the singular is intended to include the plural as well, furthermore, it is to be understood that when the terms "comprising" and/or "including" are used in this specification, it indicates that There are features, steps, operations, devices, components and/or combinations thereof.

In a first aspect, the present invention provides a system for biomass flash pyrolysis gasification and tar removal, including:

Settling furnace, providing environment for biomass pyrolysis;

The feeder is arranged on the top of the settling furnace;

The gas distribution system includes the first primary air channel, the second primary air channel and the secondary air channel, and the first primary air channel is a nitrogen channel, which is communicated with the top of the settling furnace;

The second primary air channel is a mixed gas channel of nitrogen and active gas, which is connected to the first air inlet on the side of the settling furnace. The first air inlet is arranged on the upper part of the settling furnace. mixed composition;

The secondary air passage is a mixed gas passage of nitrogen, oxygen, water vapor and carbon dioxide, and the secondary air passage is connected with the second air inlet on the side of the settling furnace, and the second air inlet is arranged at the lower part of the settling furnace.

In some embodiments, the feeder is a rotary feeder.

In some embodiments, the first air inlet is located at 3/4-6/7 of the height of the settling furnace.

In some embodiments, the second air inlet is located at 1/4-1/2 height of the settling furnace.

In some embodiments, a cyclone separator is also included, and the cyclone separator is connected to the outlet at the lower end of the settling furnace.

Further, the solid outlet of the cyclone separator is connected to the feeder at the top of the settling furnace through a pipeline.

The cyclone separator can separate the unpyrolyzed solid material, and put it back into the settling furnace for pyrolysis, so as to improve the utilization rate of biomass and improve the quality of solid carbon.

In the second aspect, the present invention provides a process for biomass flash pyrolysis gasification and tar removal, comprising the following steps:

The biomass powder is blown into the settling furnace with nitrogen as the first air;

Pass the mixed second air of nitrogen, oxygen, water vapor and carbon dioxide into the upper part of the settling furnace;

In the settling furnace, under the set temperature, the biomass powder is in an active atmosphere, the biomass powder completes high-temperature flash pyrolysis, and volatilization is analyzed;

The precipitated volatiles move downward, and under the action of the mixed secondary air of nitrogen, oxygen, water vapor and carbon dioxide introduced into the lower part of the settling furnace, thermochemical high-temperature cracking occurs, and macromolecules are cracked into small hydrocarbon gas molecules.

In some embodiments, the biomass powder has a particle size of 60 μm-300 μm. The biomass used can be pine, coconut shell, bamboo, etc.

In some embodiments, the relationship between the nitrogen flow rate carrying the biomass powder and the mass of the biomass powder is: the biomass powder concentration is 0.35-0.45 [kg biomass powder/kg primary air].

In some embodiments, in the second primary wind, the volume fraction of oxygen is 2%-10%, the volume fraction of water vapor is 10%-40%, and the volume fraction of carbon dioxide is 25%.

In some embodiments, in the secondary air, the volume fraction of oxygen is 0%-6%, the volume fraction of water vapor is 20-30%, and the volume fraction of carbon dioxide is 25%.

Further, the flow ratio of the first primary air, the second primary air and the secondary air is 1:2-4:2-3.

In some embodiments, the temperature in the settling furnace is 850-1450°C and the ramp rate is 1200-1650K s ⁻¹ .

Further, the residence time of the biomass powder in the settling furnace is 3-10s.

In a third aspect, the present invention provides the application of the biomass flash pyrolysis gasification and tar removal process or system in the gas supply of biomass power plants.

The pyrolysis gas produced by the flash pyrolysis of the system can be directly passed into the boiler of the biomass power plant as a gas for gas supply.

Example 1

As shown in Figure 1, a system for biomass flash pyrolysis gasification and tar removal includes: a biomass source 1, which processes biomass raw materials to obtain dried biomass with a particle size of 60-300 μm. Substance powder, the downstream end of which is connected to the rotary machine 3;

The gas distribution system 2 provides the required gas atmosphere. They are: a primary air supply 2L/min nitrogen to blow the biomass powder into the settling furnace device, a 6L/min nitrogen supply to carry the mixed oxygen and water vapor into the system through the vent, and the gas mixing ratio is: oxygen The volume fraction of carbon dioxide is 5%, the volume fraction of water vapor is 20%, and the volume fraction of carbon dioxide is 25%; the secondary air is: the mixed gas is carried into the system from the lower part of the settling furnace through 6L/min nitrogen, and the gas mixing ratio is: The volume fraction of oxygen is 3%, the volume fraction of water vapor is 25%, and the volume fraction of carbon dioxide is 25%. The ratio of primary and secondary air should be based on the proportion of volatile components of biomass raw materials to ensure complete flash pyrolysis of biomass and thermochemical high-temperature pyrolysis removal of tar. The primary air system of the air supply system is connected to the feeding system for feeding, and the secondary air is mixed with the active gas and then supplied to the charcoal-making system of the settling furnace;

The rotary feeder 3 supplies biomass powder through the rotary feeder, and is blown into the settling furnace system by the primary air;

In the settling furnace 4, the furnace temperature is set to 1000°C, the raw material stays in the furnace for 4s, and the heating rate is 1000K s ⁻¹ . Under the atmosphere provided by primary air, biomass powder is rapidly pyrolyzed at high temperature. The living bottom slag is received at the bottom of the furnace. The gas-solid product enters the cyclone separator;

The cyclone separator 5 separates gas-solid products, and separates incompletely pyrolyzed biomass raw materials and fixed carbon by the difference in density. Through the cyclone separator 5, the gaseous products are collected from the flue, and the solid products are collected according to the density. The cyclone is connected to the gas-solid product collection system 6 .

The gas-solid product collection device 6 includes a gas storage tank communicating with the flue of the settling furnace, and a fixed carbon collection device.

The overall process flow is:

As shown in the above process flow: the process of biomass flash pyrolysis gasification and tar removal, that is, the original biomass direct combustion process is converted into flash pyrolysis and tar removal of biomass, and the use of gas The technological process that solid product is used as fuel, it comprises the steps:

The coconut shell biomass raw material is crushed, ground and screened multiple times to obtain biomass powder with a particle size between 60 μm and 300 μm, which is used as a raw material after drying;

The required gas atmosphere is provided by the gas supply system. They are: a primary wind blowing 4.5g/min of coconut shell powder into the settling furnace device with 2L/min nitrogen gas, and a 6L/min nitrogen gas carrying the mixed oxygen and water vapor into the system through the vent, and the gas The mixing ratio is: the volume fraction of oxygen is 5%, the volume fraction of water vapor is 20%, and the volume fraction of carbon dioxide is 25%; the secondary air is: the active gas is carried by 9L/min nitrogen into the lower section of the settling furnace, and the active gas : The volume fraction of oxygen is 3%, the volume fraction of water vapor is 25%, and the volume fraction of carbon dioxide is 25%.

The principle of biomass pyrolysis is the following reaction equation:

Biomass fuel is mainly composed of three components, cellulose, hemicellulose and lignin, and its pyrolysis is assumed to be the independent pyrolysis of the three components:

1) Pyrolysis of cellulose:

2) Pyrolysis of hemicellulose:

3) Pyrolysis of lignin:

The raw materials were fed into the settling furnace through the rotary feeder, the furnace temperature was set to 1000°C, the raw materials stayed in the furnace for 4s, and the heating rate was 1000K s ⁻¹ . Under the activated atmosphere, the biomass powder completes the process of high temperature flash pyrolysis. The biomass powder is pyrolyzed, a large amount of volatile matter is precipitated, and the fixed carbon is retained.

Under the action of secondary air, the volatile matter (ie tar) desorbed by thermal desorption undergoes thermochemical high-temperature cracking, and the macromolecules are cracked into small molecular alkanes and hydrocarbon gas molecules, thereby reducing the production of tar. The pyrolysis of volatiles further promotes the flash pyrolysis of biomass powder.

The gas-solid products enter the cyclone separator from the settling furnace, the gas products are collected as gaseous fuel, the solid products are separated by the cyclone separator, the unpyrolyzed biomass is recirculated and pyrolyzed, and the biomass fixed carbon obtained from the pyrolysis is collected as a by-product .

The yield of gaseous product was about 75%, the yield of fixed carbon was 16%, and the yield of tar was too low to be collected.

The above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. A system for biomass flash pyrolysis gasification and tar removal is characterized in that: the method comprises the following steps:

a settling furnace for providing an environment for biomass pyrolysis;

the feeding machine is arranged at the top of the settling furnace;

the gas distribution system comprises a first primary air channel, a second primary air channel and a secondary air channel, wherein the first primary air channel is a nitrogen channel and is communicated with the top of the sedimentation furnace;

the second primary air channel is a mixed gas channel of nitrogen and active gas and is communicated with a first air inlet on the side surface of the settling furnace, the first air inlet is arranged on the upper part of the settling furnace, and the active gas is a mixed gas of oxygen, water vapor and carbon dioxide;

the secondary air channel is a mixed gas channel of nitrogen, oxygen, water vapor and carbon dioxide, and is connected with a second air inlet on the side surface of the settling furnace, and the second air inlet is arranged at the lower part of the settling furnace.

2. The system for flash pyrolysis gasification and tar removal of biomass according to claim 1, wherein: the feeder is a rotary feeder.

3. The system for flash pyrolysis gasification and tar removal of biomass according to claim 1, wherein: the first air inlet is arranged at the 3/4-6/7 height of the settling furnace.

4. The system for flash pyrolysis gasification and tar removal of biomass according to claim 1, wherein: the second air inlet is arranged at the 1/4-1/2 height of the settling furnace.

5. The system for flash pyrolysis gasification and tar removal of biomass according to claim 1, wherein: the cyclone separator is connected to the outlet at the lower end of the settling furnace;

further, a solid outlet of the cyclone separator is connected with a feeding machine at the top of the settling furnace through a pipeline.

6. A process for flash pyrolysis gasification and tar removal of biomass is characterized by comprising the following steps: the method comprises the following steps:

blowing biomass powder into a settling furnace by using nitrogen as first primary air;

introducing mixed secondary air of nitrogen, oxygen, water vapor and carbon dioxide into the upper part of the settling furnace;

in a settling furnace, under the set temperature and the active atmosphere of biomass powder, completing high-temperature flash pyrolysis of the biomass powder, and analyzing volatilization;

the separated volatile component moves downwards, and is subjected to thermochemical pyrolysis under the action of mixed secondary air of nitrogen, oxygen, water vapor and carbon dioxide introduced into the lower part of the settling furnace, and macromolecules are cracked into micromolecular hydrocarbon gas molecules.

7. The process for flash pyrolysis gasification and tar removal of biomass according to claim 6, wherein: the particle size of the biomass powder is 60-300 μm;

preferably, the relationship between the nitrogen flow carrying the biomass powder and the mass of the biomass powder is as follows: the concentration of the biomass powder is about 0.35-0.45kg biomass powder/kg primary air.

8. The process for flash pyrolysis gasification and tar removal of biomass according to claim 6, wherein: in the second primary air, the volume fraction of oxygen is 2-10%, the volume fraction of water vapor is 10-40%, and the volume fraction of carbon dioxide is 25%;

or in the secondary air, the volume fraction of oxygen is 0-6%, the volume fraction of water vapor is 20-30%, and the volume fraction of carbon dioxide is 25%.

9. The process for flash pyrolysis gasification and tar removal of biomass according to claim 6, wherein: the flow ratio of the first primary air to the second primary air to the secondary air is 1:2-4: 2-3;

further, the temperature in the settling furnace is 850-1450 ℃, and the heating rate is 1200-1650K s^-1；

Further, the residence time of the biomass powder in the settling furnace is 3-10 s.

10. Use of a process for flash pyrolysis gasification and tar removal of biomass according to any one of claims 6 to 9 or a system for flash pyrolysis gasification and tar removal of biomass according to any one of claims 1 to 5 in biomass power plant gas supply.

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